Abstract
Sarcoplasmic reticulum (SR) membrane vesicles derived from human atrium
were characterized by specific ryanodine binding assay and fused
into planar lipid bilayers. The tritiated form of the alkaloid bound
to its receptor with a K(D) of 2.2 nM and a Bmax of 268 fmol/mg protein
respectively. Special emphasis was placed on an anion-selective channel
present in the SR membrane, which exhibited a mean conductance value
of 67 pS when recorded in asymmetrical 50 mM trans/250 mM cis CsCl
buffer system and a sensitivity to SITS (1 to 100 microM). Single
and multiple channel activities displayed low voltage sensitivity
and variability in its gating behavior which might result in spontaneous
channel inactivation. However, the majority of the recordings (60\%)
resulted in a steady-state high open probability. The inactivated
channel could be transiently reactivated with depolarizing voltage
steps. This behavior is very similar, if not identical, to that observed
for the SR Cl$^-$ channel in ventricular cells. The inactivation
process is probably not directly related to a phosphorylation/dephosphorylation
mechanism since PKA and PKG in presence of an adequate phosphorylation
cocktail failed to reactivate the SR Cl$^-$ channel. In contrast,
the use of a monoclonal anti-phospholamban antibody allowed the inhibition
of the activity of the anionic channels. These results suggest that
the regulation of the human atrial SR Cl$^-$ channel is dependent
upon an interaction with phospholamban, which was clearly identified
in our atrial preparations by Western blot analysis using monoclonal
antibody.
- 8732504
- action
- antibodies,
- atria,
- binding,
- blocking,
- blotting,
- calcium
- calcium-binding
- cells,
- channel,
- channels,
- chloride
- cultured,
- factors,
- gov't,
- heart
- humans,
- muscle
- non-u.s.
- potentials,
- protein
- proteins,
- receptor
- release
- research
- reticulum,
- ryanodine
- sarcoplasmic
- support,
- time
- western,
Users
Please
log in to take part in the discussion (add own reviews or comments).